My SIL found out she was having a boy at 12 weeks (and she also knows of someone else who found out then too). I think the actual genitals are too small or underdeveloped to see but supposedly the facing of the pelvis can determine the sex. If the pelvis is pointing upwards it's mean to be a boy, down and likey to be a girl. They were accurate with my SIL so you maybe you can ask. I'm gonna try this time around